Answer:
1) Recollapsing universe
2) critical universe
3) Coasting universe
Explanation:
According to the smallest ration (ratio actual mass density to current density) to largest ration, rank of models for expansion of universe are
1) Recollapsing universe -in this, metric expansion of space is reverse and universe recollapses.
2) critical universe - in this, expansion of universe is very low.
3) Coasting universe - in this, expansion of universe is steady and uniform
Based on the direction of propagation compared to direction of vibration, waves are classified into:
1- Transverse waves: The direction of propagation of the wave is perpendicular to the direction of vibration of the medium particles.
2- Longitudinal waves: The direction of propagation of the wave is the same as the direction of vibration of the medium particles.
For the question we have here, since the direction of the wave is the same as the direction of vibration of particles, therefore, this wave is a longitudinal wave
D. Atoms.
Explanation:
All the matter is made of elementary particles called "atoms".
Further, an atom is made of electrons, protons and neutrons. The electrons & protons are again made of the fundamental sub-particles, electrons (leptons) and the protons(quarks).
The classification of particles is shown in the figure attached
The period of the second pendulum is 0.9 s
Explanation:
The period of a simple pendulum is given by the equation

where
L is the length of the pendulum
g is the acceleration of gravity at the location of the pendulum
For the first pendulum, we have
L = 0.64 m
T = 1.2 s
Therefore we can find the value of g at that location:

Now we can find the period of the second pendulum at the same location, which is given by

where we have
L = 0.36 m (length of the second pendulum)

Substituting,

#LearnwithBrainly
The answer:
the relationship between elementary charge, potential difference and electrical potential energy is given by
E= qV
E: lectrical potential energy
q: elementary charge
V: potential difference
but we have e=abs val(q)=3
so we have E= qV=3ex4.5V=<span>13.5 eV
</span>
the answer is <span>(4)13.5 eV</span>